# -*- coding: utf-8 -*-
def trim(s):
    try:
        while s[0] == ' ':
            s = s[1:]
        while s[-1] ==' ':
            s = s[:-2]
        return s
    except:
        return ''
    pass

# 测试:
if trim('hello  ') != 'hello':
    print('测试失败!')
elif trim('  hello') != 'hello':
    print('测试失败!')
elif trim('  hello  ') != 'hello':
    print('测试失败!')
elif trim('  hello  world  ') != 'hello  world':
    print('测试失败!')
elif trim('') != '':
    print('测试失败!')
elif trim('    ') != '':
    print('测试失败!')
else:
    print('测试成功!')
